Closest User Terminal Search Method for a Telecommunication Network and Service Node Applying Such a Method

ABSTRACT

Service node for a telecommunication network ( 15 ) and method for determining a group of n user terminals ( 21 ) which are closest to a point of interest ( 22 ). First, a search range with an upper limit ( 24 ) is set. Then in an iterative manner, a current search cell of the set of cells ( 1 - 10 ) is determined and the search cell is queried for user data. The user terminals ( 21 ) are added to a set of found user terminals, and if the set of found user terminals comprises n or more user terminals ( 21 ), the upper limit ( 24 ) of the search range is adjusted to the n th  lowest distance. This is repeated until no further possible cell ( 1 - 10 ) can be determined. The set of criteria can be set and matched with obtained user data to find a closest user terminal ( 21 ) having a specific role.

FIELD OF THE INVENTION

The present invention relates to a method of determining a group of nuser terminals in a telecommunication network which are closest to apoint of interest (e.g. nearest in a geographical sense), n being aninteger value. In a further aspect, the present invention relates to aservice node for a telecommunication network comprising a set of cellswith a predetermined coverage area servicing user terminals, in whichthe service node is connectable to an application server executing anapplication for determining a group of n user terminals which areclosest to a point of interest in the predetermined coverage area.

PRIOR ART

In some applications in a telephony network, the application searchesfor the (e.g. geographically) closest particular user of a handset to apoint of interest. This particular user may satisfy some criteria (e.g.being part of a list of medical urgency personnel) which may bedependent on the particular application. In existing telephony networksystems, this requires first to determine which users satisfy the givencriteria, determine the location of all of those users, and to determinewhich user is closest to the point of interest. All these steps requirea lot of requests and messages being transmitted in the telephonynetwork, which is expensive and claims network capacity.

SUMMARY OF THE INVENTION

The present invention seeks to provide an improved method and system, inwhich the total number of requests and messages associated with theapplication of finding a closest user terminal (or a group of closestuser terminals) is reduced.

According to the present invention, a method according to the preambledefined above is provided, comprising:

a) determining a set of cells of the network, each having an associateddistance range to the point of interest with a minimum and maximumvalue, and setting a search range with an upper limit;

b) determining a current search cell of the set of cells which has thelowest minimum value lower than the upper limit;

c) querying the current search cell for user data associated with userterminals in the current search cell (such as presence, location, etc),adding the user terminals to a set of found user terminals, and if theset of found user terminals comprises n or more user terminals adjustingthe upper limit of the search range to the n^(th) lowest distancebetween each of the user terminals in the group and the point ofinterest;

d) repeating the steps b) and c) until no further cell having a minimumvalue lower than the upper limit can be determined;

e) determining the group of n closest user terminal as the n userterminals in the queried cells having the n lowest distances to thepoint of interest.

For some applications searching for user terminals it is only relevantto find the closest relevant user terminal. The present invention makessure that the applicable user terminal is found using the cell identitywith as few user data (location) requests as possible given any userterminal distribution. The present invention also makes sure that asmany cells as possible will be excluded before doing the actual userdata (location) requests. This will result in fewer user data (location)requests and therefore less power and network resource usage. Therepetition of the steps b) and c) may be implemented by keeping trackwhich cell has already been searched and finding the cell which is nextclosest to the point of interest, or as an alternative, a lower limit ofthe search range may be set to the minimum value of the current searchcell each iteration.

In a further embodiment, setting the search range comprises setting theupper limit equal to a predetermined maximum value. In this manner, theupper limit can be set at a value independent of the coverage area ofthe set of cells, in order to limit the initial search range to amaximum value (e.g. depending on an expected time to travel from thepresent user location to the point of interest). Alternatively, aninitial search range is limited to the coverage area of the set of cellschosen to be included in the search, by setting the lower limit to thelowest minimum value and the upper limit to the highest maximum value.

In some circumstances, the set of cells may comprise two or more cellseach having an equal minimum distance value to the point of interest.For the present method, such cells are considered as a single currentsearch cell, and the lower limit is reset to this minimum value in therelevant step.

In a further embodiment, the user data comprises position data, and theposition data is used to calculate the distance between the userterminal and the point of interest. The position data may be obtained ina number of different manners, e.g. using radio triangulation (as suchknown from e.g. GSM networks), obtaining data from a GPS unit in theuser terminal, or by having the user input location data in the userterminal.

In order to enhance the efficiency of the present method, the minimumvalue of a cell is adapted to exclude an overlapping area of a furthercell closer to the point of interest in a further embodiment. In somecircumstances this will allow to exclude that cell from the user dataquery, as the adapted minimum distance to the point of interest to thecoverage area may be higher than the upper limit of the search range.

The present method may be extended to include fixed user terminals,which are e.g. connected to a fixed network, such as the public switchedtelephone network. In a further embodiment, a user terminal comprises aterminal with a fixed and known location. As the location is fixed andknown, the distance to a point of interest may be calculated andincluded in the present method embodiments.

In the embodiments of the present invention, a search may be performedfor finding a user terminal having a specific role, e.g. a user terminalin the possession of medical staff or other emergency personnel. Thedetermination whether a user terminal is a specific user terminalsatisfying a set of criteria may be implemented in various manners. Inone particular embodiment, a user terminal in a cell is added to the setof found user terminals if the associated user data obtained from thecell matches a set of criteria. By applying the criteria to the dataobtained from a cell query, it is assured that the most up to dateinformation is used for determining a specific user terminal.

In some cases it is necessary to determine more than one nearest userterminal for different roles, e.g. an ambulance and a policeman. To thisend, the present method is performed in parallel for a number ofdifferent sets of criteria, using the same current search cell for eachof the different sets of criteria. As a result, a lowest possible numberof cell queries is obtained.

In a further aspect, a service node according to the preamble definedabove is provided, in which the service node is connectable to a firstnetwork unit arranged to obtain information from the telecommunicationnetwork for determining a distance range to the point of interest with aminimum and maximum value for each of the set of cells, and to a secondnetwork unit arranged to query a cell for user data associated with theuser terminals being serviced in the cell. The second network unit maybe implemented in several network units, each providing a different kindof user data, e.g. a cell query unit providing data regarding which userterminals are in a cell and further data related to these userterminals, and a positioning unit providing location data of userterminals. The service node is arranged for

a) setting a search range with an upper limit;

b) determining a current search cell of the set of cells which has thelowest minimum value lower than the upper limit;

c) querying the second network unit for user data associated with userterminals in the current search cell, adding the user terminals to a setof found user terminals, and if the set of found user terminalscomprises n or more user terminals, adjusting the upper limit of thesearch range to the n^(th) lowest distance between each of the userterminals in the group and the point of interest;

d) repeating the steps b) and c) until no further cell having a minimumvalue lower than the upper limit can be determined; and

e) determining the group of n closest user terminal as the n userterminals in the queried cells having the n lowest distances to thepoint of interest. In further embodiments, the service node may befurther arranged to execute functions corresponding to the variousmethod embodiments discussed above.

In an even further aspect, the present invention relates to a computerprogram product comprising executable code, which when loaded in aprocessing system of a service node for a telecommunication network,provides the service node with the ability to perform embodiments of thepresent method.

Short description of drawings

The present invention will be discussed in more detail below, using anumber of exemplary embodiments, with reference to the attacheddrawings, in which

FIG. 1 shows a simplified diagram of a telecommunication network;

FIG. 2 shows an exemplary situation sketch for an application of a firstembodiment of the present method;

FIG. 3 a-3 e show one dimensional range graphs of the situation sketchof FIG. 2 for explaining a first embodiment of the present invention;

FIG. 4 shows a further exemplary situation sketch for an application ofa second embodiment of the present method;

FIG. 5 shows a one dimensional range graph of the situation sketch ofFIG. 4 for explaining a second embodiment of the present invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

In FIG. 1, a simplified diagram of a telecommunication network is shownin which embodiments of the present invention may be applied, using amobile telephony network as an exemplary embodiment. Thetelecommunication network is e.g. a GSM network, in which network cellsprovide a cellular type of geographical coverage area 15, in which anumber of user terminals 21 (e.g. mobile telephones) can be serviced. Anapplication server 11 (e.g. a personal computer or server computer) runsan application, and interfaces with a service node 20 of thetelecommunication network for obtaining data regarding the mobile userterminals 21. The service node 20 may comprise one (or more) processorsand associated memory, and is able to execute a software program storedin that memory or provided on a computer program product loadable in theservice node 20, as is known to the skilled person. The service node 20is connected to various units 12-14 of the telecommunications network. Afirst unit 12 is arranged to provide information regarding the exactgeographical area covered by each cell of the network, as well asdetails on which cells are overlapping, and how much area isoverlapping. A second unit 13 is arranged to determine for each cellwhich relevant user terminals 21 are in that cell. Which user terminal21 is a relevant user terminal 21 for a specific application, can bedetermined in various manners, as will be explained below. Finally, athird unit 14 is arranged to provide positional information in relationto the user terminals 21, e.g. in geographic coordinates. This thirdunit 14 may use one of several possibilities to obtain positionalinformation from the user terminals 21. E.g. radio triangulation may beused to determine a position using a number of cell base stations.Alternatively, the positional information may be obtained directly fromthe user terminal 21. The user terminal 21 may be equipped with alocation device (e.g. a GPS unit), or a location may be input by theuser. The units 12-14 are functional units and may be separate units inthe telecommunication network, but may also be implemented incombination in one or two units in the telecommunication network.

FIG. 2 schematically shows a part of the network coverage area 15 ofFIG. 1. A set of cells 1-10 are shown, each represented by a circularcoverage area (of which some overlap. The skilled person will understandthat other forms of coverage area for each cell may exist in reality,determined by cell antenna position and antenna environment. A point ofinterest for the embodiments of the present invention is indicated byreference numeral 22, of which the (geographical) location is assumed tobe known. The point of interest 22 is a fixed location during executionof the present method, but may be associated with a (moving) mobile userterminal. The point of interest 22 is then the actual location of themobile user terminal at the time of the start of the search according toan embodiment of the present invention. A number of user terminals A-Jare present in the coverage area of cells 1-10, in the locationsindicated.

The application running on the application server 11 may be arranged toexecute a service, in which a user terminal 21 must be found which isnearest to the point of interest 22. Further applications may existwhich require a group of n nearest user terminals 21 to be found, theimplementation of which will be discussed with reference to otherembodiments below. In the example shown, the coverage area searched islimited to the area covered by the set of cells 1-10, but it will beapparent that less or more cells of the total network may be included inthe search for the nearest user terminal 21.

The point of interest 22 may be a person in need of urgent medical care,and the relevant user terminal 21 may then be a user terminal 21 whichis known to be in the possession of a medical practitioner on duty. Inorder to be able to provide the necessary medical help as soon aspossible, of course the nearest relevant user terminal 21 most be known(and contacted).

Other types of relevant or specific user terminals 21 may be defined,using a number of context criteria (i.e. specific user terminal roles).E.g. groups of user terminals 21 may be defined for medical emergencypersonnel, fire emergency personnel, police personnel, etc. The criteriamay be determined at the start of the present method, e.g. when theapplication has established which criteria are to be used in a specificcase. The second unit 13 may be arranged to determine which userterminal 21 in which cell 1-10 is a specific user terminal 21. This canbe executed continuously in the second unit 13, but may also be executedonly after having received user terminal data in response to a cell datarequest. Most telecommunication networks will be capable of providingsuch information, although different types of networks might performthis function differently. Several alternatives exist: Cell changes arecommunicated to a central point in the network where a mapping from cellto users is maintained. In an alternative embodiment, base stations ineach cell of a cellular telephony network maintain a list of the usersthey service, which base stations can be queried by the second unit 13.In an even further alternative, a broadcast channel in thetelecommunication network is used to page all user terminals in aparticular cell 1-10 to provide the information requested by the secondunit 13.

The last alternative is applicable to GSM networks. In phase 2 of theGSM standard the SMS Cell Broadcast is defined that enables sending anSMS to all users in a particular area (GSM 03.41 and GSM 03.49). Userscan selectively accept or reject the message based on the message class.A specific emergency class can be used that is typically ignored bynormal users.

Note that there is a different cost for each of the alternatives. In thefirst alternative there is a continuous cost because each cell changemust be communicated. The second alternative does not have anyadditional cost since the base stations already have the rightinformation. The third alternative has a more variable cost for eachtime that a cell is queried.

Because each user terminal 21 is in a cell 1-10, the user terminal'sapproximate location is known (the coverage area of that cell), and thusfor each cell 1-10 a distance range to the point of interest 22 can becalculated. Only cells 1-10 that comprise relevant (or specific) userterminals 21 are evaluated. When the point of interest 22 resides in oneor more cells 1-10 that comprise relevant user terminals 21, it will bedetermined for all of these cells 1-10 which relevant user terminal 21is the closest to the point of interest 22. The distance to this userterminal 21 is the starting upper limit of a search range for evaluatingfurther cells 1-10 comprising relevant user terminals 21 that are closerto the point of interest 22 then this upper limit. The cell 1-10 that isclosest to the point of interest 22 and within the upper limit isevaluated first, because that cell 1-10 potentially comprises theclosest relevant user terminal 21. This strategy of evaluating theclosest cell 1-10 from the point of interest 22 is repeated until theclosest user terminal 21 is found.

The embodiments of the present invention relate to determining adistance from a user terminal 21 to a point of interest 22. In FIG. 3a-3 e the method according to a first embodiment of the presentinvention is explained using one dimensional graphs representing thesituation sketch of FIG. 2. For each cell 1-10, the range of possibledistances to the point of interest 22 is given as a line between aminimum value and a maximum value, and the actual distance between aspecific user terminal 21 (indicated by letters A-J) by a circle on thatline. The various cells are given in the x-direction (cell #) and thedistance to the point of interest 22 in the y direction.

The starting point for finding the closest relevant (or specific) userterminal 21 is shown in FIG. 3 a. Finding the closest relevant userterminal 21 is based on first finding the closest cell 4 to the point ofinterest 22, because this cell 4 potentially contains the closest userterminal 21 (indicated by bold line). A cell data request is transmittedin the closest cell 4 (current search cell) to determine whether anyrelevant user terminal 21 is present in cell 4, and to obtain dataassociated with the found user terminals 21. As part of the cell datarequest, a location request may be transmitted to obtain location dataregarding relevant user terminals 21.

Step 1 (see FIG. 3 b) determines the next closest cell containingpotential relevant user terminals 21, which results in cell 1 (indicatedby bold line) containing one relevant user terminal A, since the closestcell 4 (cell comprising the point of interest 22) does not contain anyrelevant user terminals 21. Again, a cell data request is transmitted toobtain data relating to relevant user terminals 21 in cell 1.

The horizontal dashed lines 23, 24 indicate the distance search rangethat remains to be searched (23 indicating the lower limit and 24 theupper limit of the search range). The closest user terminal A in cell 1forms an input to adjust the search range limits 23, 24 and tosubsequently filter out cell 2 and 9 (see dashed lines in FIG. 3 b).

In a next step again the next closest cell comprising potential relevantuser terminals 21 is determined, which results in cell 7 being found(bold line in FIG. 3 c). Another cell data request in this cell 7provides data relating to two relevant user terminals 21 F and G (FIG. 3c). The upper limit 24 of the search range is adapted to the minimumdistance of one of the relevant user terminals 21 in cell 7, in thiscase the distance to user terminal G.

In a following step (see FIG. 3 d) again the next closest cellcomprising potential relevant user terminals 21 is determined, whichresults in cell 3 containing 1 relevant user terminal C (which is foundusing a cell data request). The lower limit 23 of the search range isadapted to the minimum distance in the range of cell 3. This userterminal C is however not closer to the point of interest then the userterminal G in cell 7, and therefore the upper limit 24 of the searchrange remains at the same level.

Subsequently, again the closest cell comprising potential relevant userterminals 21 is determined (FIG. 3 e), which results in cell 5comprising one relevant user terminal D (after another cell datarequest). The lower limit 23 of the search range is adapted to thelowest value of ranges associated with cell 5. Then, the closest userterminal D in cell 5 forms input to adapt the upper limit 24 of thesearch range and to filter out the remaining cells 6, 8 and 10 (see FIG.3 e).

In the above example four steps and five location requests are requiredto determine the closest user terminal 21 (D) instead of doing alocation request to all ten user terminals A-J (or all cells 1-10) anddetermining which one of the user terminals A-J is the closest to thepoint of interest 22.

In other words, in subsequent steps, first a current search cell 1-10 isfound, which has the lowest minimum value higher than the lower limit 23and lower than the upper limit 24. In the initial run, this will be thecell in which the point of interest 22 resides, and in subsequent runs,this will exclude cells 1-10 of which the minimum distance value isoutside the search range. Then, the lower limit 23 is reset to thislowest minimum value of the current search cell. Subsequently, thecurrent search cell is queried for user data relating to user terminals21 in that cell. From the user data, the distance between a userterminal 21 and the point of interest 22 may be calculated. If a userterminal 21 is found, the upper limit 24 is adjusted to the distancefrom that user terminal 21 to the point of interest 22 (or to the lowestdistance in case of more than one specific user terminal in that cell).These subsequent steps are repeated until no further current search cellcan be found.

As an alternative to the use of the lower limit 23 of the search range,it is possible to register which of the cells 1-10 have already beensearched, and to find the cell 1-10 having the next lowest minimum valuein the next iteration.

In the case that two (or more) different cells 1-10 have an equalminimum value of the possible distance range to the point of interest22, the different cells may be regarded as a single search cell. Thelower limit 23 of the search range is adapted accordingly, and allactual cells 1-10 of the search cell are queried for user data relatedto user terminals 21.

In a further embodiment, the method is adapted to take into accountoverlapping coverage areas of neighbouring cells. A situation in whichthis is applicable is shown schematically in FIG. 4. Only three cells1-3 of the telecommunication network are shown. A point of interest 22is present in the coverage area of cell 1, in which further no relevantuser terminal 21 is present. Cell 2 has a large area of coverageoverlapping with cell 1, and cell 3 has a smaller area of overlap withcell 1. Relevant user terminal A is located within the coverage area ofcell 2, and relevant user terminal B is located within the coverage areaof cell 3. The situation is also shown as one dimensional ranges in thediagram of FIG. 5.

Usually a particular user terminal 21 is returned by exactly one cell1-3 by the second unit 13, the cell in which the user terminal 21 isbeing serviced. However, since cells 1-3 actually overlap, it ispossible that more than one cell query returns the same user terminal21. If the cell query function is capable of reflecting this, excludingthe overlapping areas can further optimize the method.

In the example shown in FIGS. 4 and 5, the point of interest 22 residesin cell 1 that does not contain any user terminals 21 (as found using acell data request), so either cell 2 or cell 3 needs to be investigatednext. The closest cell to the point of interest is cell 2. However,because it was determined that there is no relevant user in cell 1, alarge part of cell 2 can be excluded. If the intersection of cell 1 andcell 2 is excluded (as well as the intersection of cell 1 and cell 3,however small), then cell 3 is actually closer to the point of interestand therefore more interesting to search first.

As shown in FIG. 5, initially cell 1 is evaluated (and excluded asindicated by the broken line). Before doing the next evaluation, firstthe intersections with cell 1 are excluded from the remaining cells (2and 3), as indicated by the line 2-1 and 3-1 (part of the distance rangeof cell 2 and cell 3 are left out as indicated by the broken lineparts). Only after that, the next cell is selected and evaluated, whichis now cell 3 instead of cell 2. The lower limit 23 of the search rangeis adapted to the minimum considered distance of cell 3, a query foruser terminal information is sent for cell 3, and the upper limit 24 ofthe search range is adapted to the distance of user terminal B. Usingthe adapted search range, cell 2 (or cell 2-1) is excluded from furthersearch, and no location request or query is sent to cell 2.

When more than one single nearest user terminal is needed by theapplication running in the application server 11, the above embodimentsmay be executed more than once (n times) in a subsequent fashion, eachtime with exclusion of the last found then nearest user terminal 21.This assures that indeed the nearest n user terminals 21 are found.

As an alternative, the same method variants as described above forfinding a single closest user terminal may be used to determine a groupof n multiple relevant user terminals as close as possible to a point ofinterest 22 (n being an integer value). The only difference is thatfurther cells are examined until the required number of n relevant userterminals 21 is found and no cells are closer to the point of interestthan the relevant user terminal with the greatest distance to the pointof interest 22. In other words, the upper limit 24 of the search rangeis only adjusted once the required number of n relevant user terminals21 has been found, and the upper limit 24 is then adjusted to the n^(th)lowest distance between each of the relevant user terminals 21 and thepoint of interest 22.

As an example, cells 1-10 are examined for relevant user terminals 21until at least two user terminals 21 are found (and stored as a set offound user terminals 21). The found user terminal 21 that is second indistance from the point of interest 22 determines whether new cells(that have not yet been examined) exist which are closer to the point ofinterest 22 and need to be examined for relevant user terminals 21. Theset of the two closest relevant user terminals 21 is updated after eachiteration, e.g. by storing a set of found user terminals 21. Thiseventually guarantees finding the two closest relevant user terminals 21to the point of interest 22.

In the example configuration discussed above with reference to FIG. 3a-3 e, the following steps would be taken to find the two nearest userterminals 21 (n=2):

First a cell query is issued in the cell 4 nearest to the point ofinterest 22, which provides no relevant user terminals 21. The cellhaving the next lowest minimum value is cell 1, which provides userterminal A. User terminal A is added to the set of found user terminals21, and the lower limit 23 is adjusted to the minimum value of cell 1.Next, the cell 7 having the next lowest minimum value larger than thelower limit 23 is queried, and user terminals F and G are added to theset of found user terminals. As this set now comprises more than therequested two user terminals 21, the upper limit 24 is set to the secondlowest distance, i.e. the distance associated with user terminal A (fromcell 1). All found user terminals 21 may be added to the set of founduser terminals, or only the requested number of user terminals with thelowest distance to the point of interest 22 may be maintained in the setof found terminals (i.e. user terminal A and G). The further cells arequeried in a similar manner (in the order cell 3, cell 5, cell 8, cell6, cell 10) and in the final result, the two nearest user terminals Dand H remain. Although in this example it requires eight cell queries tofind the two nearest user terminals, it still provides an improvementover the otherwise required number of ten cell queries.

It could also occur that multiple different searches need to beperformed for the same point of interest, e.g. if an ambulance and apoliceman are needed for the same emergency. The present method allowsthe different searches (for different sets of criteria) to be performedsimultaneously. A query in the current search cell provides dataassociated with user terminals 21 in the current search cell, and fromthis data, it is determined whether any relevant user terminal(s) 21 foreach of the set of criteria is(are) present. By synchronizing thedifferent searches, the method is further optimized by using a singlecell query result for all searches that are performed simultaneously,reducing the number of cell queries required considerably in comparisonwith executing the method multiple times sequentially for each set ofcriteria.

The embodiments according to the present invention are able to deal withthe fact that relevant user terminals 21 can have a fixed location andare not necessarily mobile user terminals 21. For this it is necessarythat the cell query function as discussed above in relation to thevarious embodiments, returns data associated with relevant userterminals 21 with a fixed location as well as relevant mobile userterminals 21. This can e.g. be implemented by assigning a fixed userterminal 21 to a list of relevant user terminals 21 of the cell coveringthe geographical location of the fixed user terminal 21. Also, as analternative, the distances between a (limited) list of fixed userterminals 21 and the point of interest 22 are determined beforehand, andare used in the method for determining the closest relevant userterminal 21.

The embodiments of the present invention are based on the assumptionthat it is possible to query which user terminals 21 reside in aparticular cell 1-10. Most networks will be capable of providing suchinformation, although different types of networks might perform thisfunction differently. Several alternatives exist as described above. Inthe case that cell changes are communicated to a central point where amapping from cell to user terminals is maintained then the cost can bederived as follows.

It shall be noted that user terminals that are of no interest will notcause any cell change events and are therefore not included in the‘subscribed users’ (n).

The following table shows what parameters have impact on the cost in thenetwork of this invention compared with traditional location requests.

Identifier Description n # of users subscribed to a service using thismethod c # of cell changes per second per subscribed user (=cell changerate) e # of cells in the network a # of cells used in the method s # ofservice requests per second (=service request rate) C Cell change cost LLocation request cost

Note that ‘a’ (the number of cells used in method) decreases as thenumber of users increases, because a subscribed user is found sooner.This means that the more subscribed users the fewer cells need to beexamined, because more cells contain subscribed users.

The equation below describes the cost when the embodiments of thepresent invention are not used and a location request shall be done persubscribed user:

OldLocationRequestCost=n*s*L

The total cost of cell changes of all subscribed users is given as:

CellChangeCost=n*c*C

The equation below describes the location request cost for allsubscribed users:

${NewLocationRequestCost} = {{CellChangeCost} + {n*s*\frac{a}{e}*L}}$${NewLocationRequestCost} = {n*\left( {c*C*\frac{s*a*L}{e}} \right)}$

The equation below shows the profit per subscribed user:

Profit = OldLocationRequestCost − NewLocationRequestCost${Profit} = {\left( {s*L} \right) - \left( {c*C*\frac{s*a*L}{e}} \right)}$

The number of subscribed users (n) and the number of cells to beevaluated (a) in relation with the number of service requests (s)together determine whether the invention brings a profit or loss for thecustomer.

Also the difference in cost of a location request (L) and a cell change(C) can have a significant impact in profit/loss result.

For some applications in telecommunications networks searching forrelevant user terminals 21 it is only relevant to find the closestrelevant user terminal 21. The various embodiments of the presentinvention make sure that the applicable user terminal 21 is found usingthe cell identity (1-10) with as few location requests as possible givenany user distribution. The various embodiments of the present inventionalso make sure that as many cells 1-10 as possible will be excludedbefore doing the actual location requests. This will result in fewerlocation requests and therefore less power and network resource usage.

The present invention has been explained above with reference to anumber of exemplar embodiments. As will be apparent to the personskilled in the art, various modifications and amendments can be madewithout departing from the scope of the present invention, as defined inthe appended claims.

1. A method of determining a group of n user terminals in atelecommunication network d which are closest to a point of interest, nbeing an integer value, the method comprising: a) determining a set ofcells of the network, each having an associated distance range to thepoint of interest (with a minimum and maximum value, and setting asearch range with an upper limit; b) determining a current search cellof the set of cells which has the lowest minimum value lower than theupper limit; c) querying the current search cell for user dataassociated with user terminals in the current search cell, adding theuser terminals to a set of found user terminals, and if the set of founduser terminals comprises n or more user terminals, adjusting the upperlimit of the search range to the n^(th) lowest distance between each ofthe user terminals in the group and the point of interest; d) repeatingthe steps b) and c) until no further cell having a minimum value lowerthan the upper limit can be determined; and e) determining the group ofn closest user terminals A as the n user terminals in the queried cellshaving the n lowest distances to the point of interest A.
 2. The methodaccording to claim 1, in which setting the search range comprisessetting the upper limit equal to a predetermined maximum value.
 3. Themethod according to claim 1, in which the current search cell comprisesone or more cells having an equal minimum value.
 4. The method accordingto claim 1, in which the user data comprises position data, and in whichthe position data is used to calculate the distance between the userterminal and the point of interest.
 5. The method according to claim 1,in which the minimum value of a cell is adapted to exclude anoverlapping area of a further cell closer to the point of interest. 6.The method according to claim 1, in which a user terminal m comprises aterminal with a fixed and known location.
 7. The method according toclaim 1, in which a user terminal in a cell is only added to the set offound user terminals if the associated user data obtained from thecurrent search cell matches a set of criteria.
 8. The method accordingto claim 7, in which the method is performed in parallel for a number ofdifferent sets of criteria, using the same current search cell for eachof the different sets of criteria.
 9. A service node for atelecommunication network comprising a set of cells with a predeterminedcoverage area servicing user terminals, in which the service node isconnected to an application server executing an application fordetermining a group of n user terminals which are closest to a point ofinterest in the predetermined coverage area, n being an integer value,the service node comprising: means for connecting to a first networkunit arranged to obtain information from the telecommunication networkfor determining a distance range to the point of interest with a minimumand maximum value for each one of the set of cells, and a second networkunit arranged to query a cell for user data associated with the userterminals being serviced in the cell; and means associated with theservice node for: a) setting a search range with an upper limit; b)determining a current search cell of the set of cells which has thelowest minimum value lower than the upper limit; c) querying the secondnetwork unit for user data associated with user terminals in the currentsearch cell, adding the user terminals to a set of found user terminals,and if the set of found user terminals comprises or more user terminalsadjusting the upper limit of the search range to the n^(th) lowestdistance between each of the user terminals in the group and the pointof interest d) repeating the steps b) and c) until no further cellhaving a minimum value lower than the upper limit can be determined; ande) determining the group of n closest user terminals as the n userterminals in the queried cells having the n lowest distances to thepoint of interest
 10. The service node according to claim 9, in whichthe service node is arranged to set the upper limit equal to apredetermined maximum value.
 11. The service node according to claim 9,in which the current search cell comprises one or more cells having anequal minimum value.
 12. The service node according to claim 9, in whichthe second network unit is arranged to obtain user data which comprisesposition data, and in which the service node is further arranged to usethe position data to calculate the distance between the user terminaland the point of interest.
 13. The service node according to claim 9, inwhich the service node is further arranged to adapt the minimum value ofa cell to exclude an overlapping area of a further cell closer to thepoint of interest.
 14. The service node according to claim 9, in which auser terminal comprises a terminal with a fixed and known location. 15.The service node according to claim 9, in which the service node isfurther arranged to add a user terminal to the set of found userterminals if the associated user data obtained from the second networkunit matches a set of criteria.
 16. The service node according to claim15, in which the service node is arranged to execute multiple searchesin parallel for a number of different sets of criteria, using the samecurrent search cell for each of the different sets of criteria. 17.(canceled)